This is quick first draft of a high current capacitor discharge circuit, to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on what to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike

"amdx"


** Keeping the things away from this reckless cretin would be a good start.




...... Phil

Now why would you treat IGBTs like SCRs, of all things? IGBTs have
MOSFET-style inputs!

If your IGBTs have internal diodes, then you can easily short the load (cap
+ inductor) and let it all ring down for a couple of cycles. A fast gate
risetime would be wise, perhaps a ZTX651 emitter follower per gate, with
probably about as much gate resistance as you have (no 100 ohm to ground, I
don't even know what make you think of that). 15V should be enough supply.
A 680 ohm pull-up resistor, or a PNP collector, can be used to pull the
ZTX651 up to turn on the IGBTs. In fact, yeah, one 2N3906 would suffice to
pull up a ZTX651 for each IGBT. Then you can use 1k pull-downs on the
ZTX651 base and emitters to discharge things, well after the action has
dissipated. You might use a couple ms one-shot timer to ensure a solid
firing.

Have you yet calculated the peak voltage, current, oscillation period,
etc.? You kind of maybe will just a little bit want to know what those are
before you even lay anything out, lest it all be an expensive exercise in
futility. . . .

Tim

P.S. Use GIF or PNG for line drawings...

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
This is quick first draft of a high current capacitor discharge circuit,
to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on what
to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike

"Tim Williams" wrote in message
...
Now why would you treat IGBTs like SCRs, of all things? IGBTs have
MOSFET-style inputs!

If your IGBTs have internal diodes, then you can easily short the load
(cap
+ inductor) and let it all ring down for a couple of cycles. A fast gate
risetime would be wise, perhaps a ZTX651 emitter follower per gate, with
probably about as much gate resistance as you have (no 100 ohm to ground,
I
don't even know what make you think of that). 15V should be enough
supply.
A 680 ohm pull-up resistor, or a PNP collector, can be used to pull the
ZTX651 up to turn on the IGBTs. In fact, yeah, one 2N3906 would suffice
to
pull up a ZTX651 for each IGBT. Then you can use 1k pull-downs on the
ZTX651 base and emitters to discharge things, well after the action has
dissipated. You might use a couple ms one-shot timer to ensure a solid
firing.

Have you yet calculated the peak voltage, current, oscillation period,
etc.? You kind of maybe will just a little bit want to know what those
are
before you even lay anything out, lest it all be an expensive exercise in
futility. . . .

Tim

P.S. Use GIF or PNG for line drawings...

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
This is quick first draft of a high current capacitor discharge circuit,
to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on what
to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike




Thanks Tim,

Let me start with your last sentence first, expensive is what I'm trying
to prevent.

I found a UPS at a metal scrap yard, a salvaged the SCR, IGBTs, capacitors
and several other parts from it. So right now I have $10.00 into the
project. I want to protect the IGBTs because I wouldn't spend the money to
purchase these new, They're probably $100.00 each.

Now your first sentence, "why would you treat IGBTs like SCRs, of all
things?"

I don't understand the question, if it's because I'm using them as a switch,
Well, it's

the high current semiconductor I have at hand.



The IGBTs do have internal diodes. Yes I agree I want a fast rise time.

You say, "perhaps a ZTX651 emitter follower per gate."



So you think I should drive each gate separately?



Then you said,

"(no 100 ohm to ground, I don't even know what made you think of that).

I started testing these IGBTs and the first few tested shorted, then I
realized I was testing them with the gate floating. So I pulled it to ground
with a resistor. Then they operated as expected. That's why I put the
resistor to ground.

Is your opinion it to small or not needed?



Now regarding "exercise in futility" it may be, I have since searched
schematics of can crushers, ring *******, etc, and see they use high
voltages across there inductors, and often a sparkgap as the switch.

More on the order of 10kv, not 450v.



Any thoughts on how to protect the IGBTs from ringing voltages.

Thanks for your input,

Mike

On Mon, 10 Mar 2008 10:52:38 -0500, "amdx" wrote:

snip
Thanks Tim,

Let me start with your last sentence first, expensive is what I'm trying
to prevent.

I found a UPS at a metal scrap yard, a salvaged the SCR, IGBTs, capacitors
and several other parts from it. So right now I have $10.00 into the
project. I want to protect the IGBTs because I wouldn't spend the money to
purchase these new, They're probably $100.00 each.

Now your first sentence, "why would you treat IGBTs like SCRs, of all
things?"

I don't understand the question, if it's because I'm using them as a switch,
Well, it's

the high current semiconductor I have at hand.



The IGBTs do have internal diodes. Yes I agree I want a fast rise time.

You say, "perhaps a ZTX651 emitter follower per gate."



So you think I should drive each gate separately?



Then you said,

"(no 100 ohm to ground, I don't even know what made you think of that).

I started testing these IGBTs and the first few tested shorted, then I
realized I was testing them with the gate floating. So I pulled it to ground
with a resistor. Then they operated as expected. That's why I put the
resistor to ground.

Is your opinion it to small or not needed?



Now regarding "exercise in futility" it may be, I have since searched
schematics of can crushers, ring *******, etc, and see they use high
voltages across there inductors, and often a sparkgap as the switch.

More on the order of 10kv, not 450v.



Any thoughts on how to protect the IGBTs from ringing voltages.

Thanks for your input,

Mike


Unless you need to turn the IGBTs off before the pulse ends an SCR would be a much better choice.
Perhaps you could scrounge around the scrapyard some more and find one for cheap.

I suspect that Tim was refering to the way you thought of to drive the gates by discharging a cap
into them. That is sometimes done to trigger an SCR and I've never seen it done to turn IGBTs on.

If you must use the IGBTs then yes, you will have much better luck driving each gate with it's own
high current driver.

The easiest way to protect from reverse voltages is to simply put a huge diode across the the coil
and let it absorb the neg swings when it rings down. Not an elegant solution, but it will work.
I know because I've done it.

Mike


"In view of such harmony in the cosmos which I,
with my limited human mind, am able to recognize,
there are yet people who say there is no God.
But what really makes me angry is that they quote
me for the support of such views."
Albert Einstein (theoretical Physicist)

"Mike" wrote in message
...
On Mon, 10 Mar 2008 10:52:38 -0500, "amdx" wrote:

snip
Thanks Tim,

Let me start with your last sentence first, expensive is what I'm
trying
to prevent.

I found a UPS at a metal scrap yard, a salvaged the SCR, IGBTs,
capacitors
and several other parts from it. So right now I have $10.00 into the
project. I want to protect the IGBTs because I wouldn't spend the money
to
purchase these new, They're probably $100.00 each.

Now your first sentence, "why would you treat IGBTs like SCRs, of all
things?"

I don't understand the question, if it's because I'm using them as a
switch,
Well, it's

the high current semiconductor I have at hand.



The IGBTs do have internal diodes. Yes I agree I want a fast rise time.

You say, "perhaps a ZTX651 emitter follower per gate."



So you think I should drive each gate separately?



Then you said,

"(no 100 ohm to ground, I don't even know what made you think of that).

I started testing these IGBTs and the first few tested shorted, then
I
realized I was testing them with the gate floating. So I pulled it to
ground
with a resistor. Then they operated as expected. That's why I put the
resistor to ground.

Is your opinion it to small or not needed?



Now regarding "exercise in futility" it may be, I have since searched
schematics of can crushers, ring *******, etc, and see they use high
voltages across there inductors, and often a sparkgap as the switch.

More on the order of 10kv, not 450v.



Any thoughts on how to protect the IGBTs from ringing voltages.

Thanks for your input,

Mike


Unless you need to turn the IGBTs off before the pulse ends an SCR would
be a much better choice.
Perhaps you could scrounge around the scrapyard some more and find one for
cheap.

I suspect that Tim was refering to the way you thought of to drive the
gates by discharging a cap
into them. That is sometimes done to trigger an SCR and I've never seen it
done to turn IGBTs on.

If you must use the IGBTs then yes, you will have much better luck driving
each gate with it's own
high current driver.

The easiest way to protect from reverse voltages is to simply put a huge
diode across the the coil
and let it absorb the neg swings when it rings down. Not an elegant
solution, but it will work.
I know because I've done it.

Mike

Hi Mike,
I liked the cap driving the gates because once the current stops flowing
the SCR shuts off. I figured I could size the cap to set my
ON time.
Regarding the reverse diode, the IGBTs have a diode built in.
Is the internal diode a fast diode? Also I see mosfets and IGBTs have these
body diodes, are they purposely built in or are they part of the
manufacturing process?
Thanks, Mike

"Tim Williams" wrote in message
...
Now why would you treat IGBTs like SCRs, of all things? IGBTs have
MOSFET-style inputs!

If your IGBTs have internal diodes, then you can easily short the load
(cap
+ inductor) and let it all ring down for a couple of cycles. A fast gate
risetime would be wise, perhaps a ZTX651 emitter follower per gate, with
probably about as much gate resistance as you have (no 100 ohm to ground,
I
don't even know what make you think of that). 15V should be enough
supply.
A 680 ohm pull-up resistor, or a PNP collector, can be used to pull the
ZTX651 up to turn on the IGBTs. In fact, yeah, one 2N3906 would suffice
to
pull up a ZTX651 for each IGBT. Then you can use 1k pull-downs on the
ZTX651 base and emitters to discharge things, well after the action has
dissipated. You might use a couple ms one-shot timer to ensure a solid
firing.

Have you yet calculated the peak voltage, current, oscillation period,
etc.? You kind of maybe will just a little bit want to know what those
are
before you even lay anything out, lest it all be an expensive exercise in
futility. . . .

Tim

P.S. Use GIF or PNG for line drawings...

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
This is quick first draft of a high current capacitor discharge circuit,
to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on what
to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike

Hi Tim,
Is this the schematic you tried to describe to me?
Thanks, Mike

Uh, you drew the PNPs backwards.

It doesn't make much difference, but it is more traditional to leave the
gates alone aside from the small gate resistors. I would draw the 1k
gate-ground resistors on the ZTX651 emitters.

I suggest you put more research into understanding what happens when you
connect a charged capacitor to an inductor. Come up with some numbers,
estimates and stuff and we'll talk some more. I think you will discover
why most "can crushers" use very large SCRs or trigatrons, higher voltages
and much higher currents. There are issues far more powerful, complicated
and dangerous than drawing PNP transistors backwards. This isn't a
beginner's project.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...

"Tim Williams" wrote in message
...
Now why would you treat IGBTs like SCRs, of all things? IGBTs have
MOSFET-style inputs!

If your IGBTs have internal diodes, then you can easily short the load
(cap
+ inductor) and let it all ring down for a couple of cycles. A fast
gate
risetime would be wise, perhaps a ZTX651 emitter follower per gate,
with
probably about as much gate resistance as you have (no 100 ohm to
ground,
I
don't even know what make you think of that). 15V should be enough
supply.
A 680 ohm pull-up resistor, or a PNP collector, can be used to pull the
ZTX651 up to turn on the IGBTs. In fact, yeah, one 2N3906 would
suffice
to
pull up a ZTX651 for each IGBT. Then you can use 1k pull-downs on the
ZTX651 base and emitters to discharge things, well after the action has
dissipated. You might use a couple ms one-shot timer to ensure a solid
firing.

Have you yet calculated the peak voltage, current, oscillation period,
etc.? You kind of maybe will just a little bit want to know what those
are
before you even lay anything out, lest it all be an expensive exercise
in
futility. . . .

Tim

P.S. Use GIF or PNG for line drawings...

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
This is quick first draft of a high current capacitor discharge
circuit,
to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on
what
to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike

Hi Tim,
Is this the schematic you tried to describe to me?
Thanks, Mike

"Tim Williams" wrote in message
...
Uh, you drew the PNPs backwards.

It doesn't make much difference, but it is more traditional to leave the
gates alone aside from the small gate resistors. I would draw the 1k
gate-ground resistors on the ZTX651 emitters.

I suggest you put more research into understanding what happens when you
connect a charged capacitor to an inductor. Come up with some numbers,
estimates and stuff and we'll talk some more. I think you will discover
why most "can crushers" use very large SCRs or trigatrons, higher voltages
and much higher currents. There are issues far more powerful, complicated
and dangerous than drawing PNP transistors backwards. This isn't a
beginner's project.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...

"Tim Williams" wrote in message
...
Now why would you treat IGBTs like SCRs, of all things? IGBTs have
MOSFET-style inputs!

If your IGBTs have internal diodes, then you can easily short the load
(cap
+ inductor) and let it all ring down for a couple of cycles. A fast
gate
risetime would be wise, perhaps a ZTX651 emitter follower per gate,
with
probably about as much gate resistance as you have (no 100 ohm to
ground,
I
don't even know what make you think of that). 15V should be enough
supply.
A 680 ohm pull-up resistor, or a PNP collector, can be used to pull the
ZTX651 up to turn on the IGBTs. In fact, yeah, one 2N3906 would
suffice
to
pull up a ZTX651 for each IGBT. Then you can use 1k pull-downs on the
ZTX651 base and emitters to discharge things, well after the action has
dissipated. You might use a couple ms one-shot timer to ensure a solid
firing.

Have you yet calculated the peak voltage, current, oscillation period,
etc.? You kind of maybe will just a little bit want to know what those
are
before you even lay anything out, lest it all be an expensive exercise
in
futility. . . .

Tim

P.S. Use GIF or PNG for line drawings...

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
This is quick first draft of a high current capacitor discharge
circuit,
to
be used for a can crusher, ring thrower or rail launcher.
I want to know how to protect my IGBTs. I'm looking for advice on
what
to
put where to save the IGBTs.
What is the best way to drive the gates, in parallel or with seperate
drivers?
I have 8 IGBTs, 600v 200amp (400amp @1ms)
Thanks, Mike

Hi Tim,
Is this the schematic you tried to describe to me?
Thanks, Mike



Did I get any closer with the schematic this time?
Yes, I've pretty much decided the application uses high voltage pulse type
caps.
I guess I need to pull out the neon sign transformers and build a spark gap.
Hmm..
Thanks for your help,
Mike

"amdx" wrote in message
...
Did I get any closer with the schematic this time?

Yes. Note that the input needs to be current-limited for each 3906, and
only one 3906 is necessary (the ZTX651 bases can be connected together).

Tim

P.S. Please snip your replies. On first look I wondered if you had even
replied anything.

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

"amdx" wrote in message
...
Hi Tim,
Is this the schematic you tried to describe to me?
Did I get any closer with the schematic this time?
Yes, I've pretty much decided the application uses high voltage pulse type
caps.
I guess I need to pull out the neon sign transformers and build a spark
gap.
Hmm..

Or a diode capicator bridge to crank the voltage similar to a High Voltage
bridge on a TV.... and use a big diode across the coil ... or not.

On Mon, 17 Mar 2008 14:09:44 -0700, RoyLFuchs
wrote:

On Thu, 13 Mar 2008 05:09:56 GMT, "William Hayes"
wrote:


"amdx" wrote in message
.. .
Hi Tim,
Is this the schematic you tried to describe to me?
Did I get any closer with the schematic this time?
Yes, I've pretty much decided the application uses high voltage pulse type
caps.
I guess I need to pull out the neon sign transformers and build a spark
gap.
Hmm..

Or a diode capicator bridge to crank the voltage similar to a High Voltage
bridge on a TV.... and use a big diode across the coil ... or not.


You're a ****ing retard, and you should stay out of groups in which you
know nothing about the topic, like these electronics groups.

Crap, The sinking turd is back :-(

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

America: Land of the Free, Because of the Brave

On Tue, 18 Mar 2008 12:29:38 -0600, "Tim Williams"
wrote:

"RoyLFuchs" wrote in message
.. .
**** off, fat ass. snip

Wow, that was refreshing!

Gosh Jim, it'll take like two million "liberal weenie"'s to get him back
for that! You may just have to work on a new saying to keep your street
cred against dickheads like this!

Tim

He changed his persona and got thru my Agent filters, for one message
only. Now that I have nfilter in place, RoyLFuchs is now
RoyL-is-****ed ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

America: Land of the Free, Because of the Brave

"RoyLFuchs" wrote in message
...
**** off, fat ass. snip

Wow, that was refreshing!

Gosh Jim, it'll take like two million "liberal weenie"'s to get him back
for that! You may just have to work on a new saying to keep your street
cred against dickheads like this!

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

Jim Thompson wrote:

On Tue, 18 Mar 2008 12:29:38 -0600, "Tim Williams"
wrote:

"RoyLFuchs" wrote in message
.. .
**** off, fat ass. snip

Wow, that was refreshing!

Gosh Jim, it'll take like two million "liberal weenie"'s to get him back
for that! You may just have to work on a new saying to keep your street
cred against dickheads like this!

Tim

He changed his persona and got thru my Agent filters, for one message
only. Now that I have nfilter in place, RoyLFuchs is now
RoyL-is-****ed ;-)


If your news server has the NTTP posting host in the header, try this
filter:

* drop NNTP-Posting-Host:72.197.139.29* to block him, no matter what
name he uses.



* drop Path:*POSTED!53ab2750!not-for-mail will drop him, and every other
user from Cox cable.

--
aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file
* drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

http://improve-usenet.org/index.html

"RoyLFuchs" wrote in message
news
On Thu, 13 Mar 2008 05:09:56 GMT, "William Hayes"
wrote:
Or a diode capicator bridge to crank the voltage similar to a High Voltage
bridge on a TV.... and use a big diode across the coil ... or not.
I'm a ****ing retard, and I should stay out of groups in which I
know nothing about the topic, like these electronics groups.

You got my vote.